Divisor 15993

To determine if any number is divisible by 15993, you must apply 2 tests successively. If all of them 'pass' - that is, if your number is divisible by 9 and 1777 - then it is divisible by 15993.

The following tests must pass:

• Test if a number is divisible by 9
• The "Nance Test" for Divisibility by 1777

Easy!